For many applications, heat is transferred or dissipated to the ambient through conduction and air convection. In order to increase the power of a system, it is necessary to increase the heat dissipation capabilities of the system. Because the convection heat transfer coefficient is commonly the system limitation, extending the heat transfer area can increase the rate of heat dissipation. An example of this is a radiator. Connecting the radiator to a system heat source can increase the heat transfer area through which heat can be rejected to the ambient. As the radiator size (i.e., surface area) increases, its capability to dissipate heat increases allowing the accommodation of larger system power loads.
The current trend is to design electronic systems to provide more powerful systems in smaller package sizes. In contrast to the previous discussion, this trend signifies increased heat loads and dissipation needs while decreasing the package size and thus the package area available for heat dissipation. Consequently, improving the heat transfer from the heat source of a system to the ambient becomes a significant consideration for this kind of application. In particular, high performance microprocessors, especially power-limited chips, dissipate very significant power, leading to significant average heat fluxes over the entire chip area (˜70-100 W/cm2) as well as ultra high local heat fluxes at the location of hot spots (˜200-500 W/cm2).